Preparation method of rod-shaped calcium carbonate

Abstract

A method for preparing rod-shaped calcium carbonate includes: mixing converter slag and ammonium salt aqueous solution for extraction; removing insoluble substances in the extraction process to obtain a reaction solution containing calcium ions, magnesium ions and barium ions, wherein the calcium ion concentration is 0.1 to 5% by weight; in a high-gravity reaction device with a rotation speed of 300 to 600 rpm, contacting the reaction solution with a carbon source for a precipitation reaction to form a calcium carbonate slurry; and separating to obtain the rod-shaped calcium carbonate. Through the preparation method of the present disclosure, the prepared rod-shaped calcium carbonate has the characteristics of high purity, and thus has application prospects in many fields such as rubber, plastics, papermaking, ink, coatings, and medicine.

Description

Technical Field

[0001] The present disclosure relates to a method for preparing calcium carbonate particles, and particularly to a method for preparing light calcium carbonate particles with a rod-like structure. Background Art

[0002] Calcium carbonate is a common inorganic material in industrial production and is widely used in fields such as rubber, plastics, papermaking, printing ink, coatings, and medicine to improve the stability, hardness, rigidity, heat resistance, and processing performance of products, and has the advantage of low cost.

[0003] In terms of morphology, calcium carbonate also has differences in cube, prism, sphere, and needle shapes, and different morphologies have different applications. Among them, rod-shaped calcium carbonate has a wide range of uses due to its high aspect ratio. When used as a filler in papermaking, rod-shaped calcium carbonate can improve the bulkiness, gloss, and printing adaptability of paper; when used in paper coatings, due to the bridging effect that can be generated between rod-shaped calcium carbonate and paper fibers, the resulting paper has better gloss and higher strength; when used as a filler in plastics, rod-shaped calcium carbonate can effectively improve the impact resistance and flexural strength of plastics; when applied to the rubber field, especially in the tire process, its reinforcing performance is more significant.

[0004] However, the common method for preparing rod-shaped calcium carbonate is to control the crystal morphology of the prepared calcium carbonate by means of a relatively high reaction temperature, or by using a crystal form control agent or crystal seeds (such as aragonite calcium carbonate or other rod-shaped materials). However, there are residual problems with the crystal form control agent or crystal seeds, resulting in a decrease in the purity of the product, which in turn affects the mechanical properties of the product; while the process of high reaction temperature causes problems of increased energy consumption and high production costs, making it difficult to scale up production.

[0005] In view of this, it is necessary to propose a method for preparing rod-shaped calcium carbonate with improved high-purity process to meet the actual requirements of current applications and production preparations. Summary of the Invention

[0006] A method for preparing rod-shaped calcium carbonate includes: mixing converter slag and an ammonium salt aqueous solution for extraction; removing insoluble substances in the extraction process to obtain a reaction solution containing calcium ions, magnesium ions, and barium ions, wherein the calcium ion concentration is 0.1 to 5% by weight; in a high-gravity reaction device with a rotation speed of 300 to 600 rpm, bringing the reaction solution into contact with a carbon source for a precipitation reaction to form a calcium carbonate slurry; and separating the liquid in the calcium carbonate slurry to obtain the rod-shaped calcium carbonate.

[0007] According to the present disclosure, through the operation of the supergravity device and the selection of raw materials, the process of the present disclosure can produce high-purity rod-shaped calcium carbonate at normal temperature and pressure without using any additives (such as crystal form control agents or seeds), so it has application prospects in many fields such as rubber, plastics, papermaking, ink, coatings, and medicine.

[0008] Furthermore, since the manufacturing method of the present disclosure does not use any additives such as crystal form control agents or seeds and the solvent composition is simple, the solvent can be recovered and reused, and the process improvement effect can be achieved.

[0009] On the other hand, the raw materials of the manufacturing method of the present disclosure adopt the by-products generated from steel smelting, so it has more competitive advantages in terms of raw material cost compared with the prior art.

[0010] Generally speaking, the preparation process of the rod-shaped calcium carbonate manufacturing method of the present disclosure is simple, environmentally friendly, and there is no concern about the residue of additives in its products, and it has the value of industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The embodiments of the present disclosure are illustrated by exemplary reference drawings:

[0012] Figure 1 is a flowchart of the method for preparing rod-shaped calcium carbonate of the present disclosure;

[0013] Figure 2 is a cross-sectional schematic view of the supergravity reaction device of the present disclosure;

[0014] Figure 3 is a schematic view of the reaction system with the supergravity reaction device of the present disclosure;

[0015] Figure 4 is a flowchart of another method for preparing rod-shaped calcium carbonate of the present disclosure;

[0016] Figure 5 is another schematic view of the reaction system with the supergravity reaction device of the present disclosure;

[0017] Figure 6 is a scanning electron microscope image of the product of Example 1 of the present disclosure;

[0018] Figure 7 is a scanning electron microscope image of the product of Comparative Example 1 of the present disclosure;

[0019] Figure 8A is a scanning electron microscope image of the calcium carbonate particles after the precipitation reaction of Example 2 of the present disclosure; Figure 8B is a scanning electron microscope image of the re-precipitated product of Example 2 of the present disclosure;

[0020] Figure 9AScanning electron microscope image of calcium carbonate particles after precipitation reaction in Example 3 of the present disclosure; Figure 9B Scanning electron microscope image of the product in Example 3 of the present disclosure;

[0021] Figure 10 Scanning electron microscope image of the product in Comparative Example 2 of the present disclosure;

[0022] Figure 11 Scanning electron microscope image of the product in Comparative Example 3 of the present disclosure;

[0023] Figure 12 Scanning electron microscope image of the product in Comparative Example 4 of the present disclosure;

[0024] Figure 13 Scanning electron microscope image of the product in Comparative Example 5 of the present disclosure;

[0025] Figure 14 Scanning electron microscope image of the product in Comparative Example 6 of the present disclosure;

[0026] Figure 15 Scanning electron microscope image of the product in Comparative Example 7 of the present disclosure;

[0027] Figure 16 Scanning electron microscope image of the product in Comparative Example 8 of the present disclosure;

[0028] Figure 17 Scanning electron microscope image of the product in Comparative Example 9 of the present disclosure;

[0029] Figure 18 Scanning electron microscope image of the product in Comparative Example 10 of the present disclosure;

[0030] Figure 19 Scanning electron microscope image of the product in Comparative Example 11 of the present disclosure;

[0031] Figure 20 Scanning electron microscope image of the product in Comparative Example 12 of the present disclosure;

[0032] Figure 21 Scanning electron microscope image of the product in Comparative Example 13 of the present disclosure;

[0033] Figure 22 Scanning electron microscope image of the product in Comparative Example 14 of the present disclosure;

[0034] Figure 23 Scanning electron microscope image of the product in Comparative Example 15 of the present disclosure;

[0035] Figure 24 Scanning electron microscope image of the product in Comparative Example 16 of the present disclosure;

[0036] Figure 25 Scanning electron micrograph of the article of Comparative Example 17 of the present disclosure; and

[0037] Figure 26 Scanning electron micrograph of the article of Comparative Example 18 of the present disclosure.

[0038] Wherein, reference numerals:

[0039] 1: High gravity reaction device

[0040] 10: Housing

[0041] 11: Rotating disk

[0042] 12: Motor drive

[0043] 13: Infusion tube

[0044] 14: Feed inlet

[0045] 15: Drain pipe

[0046] 2: Carbon source supply device

[0047] 31: Mixing tank

[0048] 32, 4, 52: Solid-liquid separation equipment

[0049] 51: Sedimentation tank

[0050] 5, 6: Rod-shaped calcium carbonate

[0051] S11 - S14, S21 - 25: Steps. Detailed implementation manners

[0052] The following specific embodiments illustrate the implementation manners of the present disclosure. Those skilled in the art can easily understand the advantages and effects of the present disclosure from the content described in this specification. The present disclosure can also be implemented or applied through other different implementation manners. All details in this specification can also be given different modifications and changes based on different viewpoints and applications without departing from the spirit described in the present disclosure. In addition, all ranges and values herein are inclusive and combinable. Any numerical value or point falling within the ranges described herein, such as any integer, can be used as the minimum or maximum value to derive sub-ranges, etc.

[0053] Please refer to Figure 1, which illustrates the process flow of the method for preparing rod-shaped calcium carbonate of the present disclosure. First, converter slag and an ammonium salt aqueous solution are mixed for extraction (step S11); then, the insoluble substances in the extraction process are removed to obtain a reaction solution containing calcium ions, magnesium ions, and barium ions (step S12); in a high-gravity reaction device with a rotation speed of 300 to 600 rpm, the reaction solution and a carbon source are subjected to a precipitation reaction (step S13) to form a calcium carbonate slurry; and the liquid in the calcium carbonate slurry is separated to obtain rod-shaped calcium carbonate (step S14).

[0054] In the text, the "extraction" process uses an aqueous solution dissolved with an ammonium salt as the extraction solvent, disperses or dissolves the converter slag material in the extraction solvent, and dissolves calcium ions, magnesium ions, and barium ions in the converter slag. After that, after solid-liquid separation of the insoluble substances in the extraction process, the obtained extraction liquid is the reaction solution. In a specific embodiment, the volume molar concentration of the ammonium salt in the ammonium salt aqueous solution is 0.01 to 3 M, and the extraction time is controlled within the range of 0.5 to 1 hour to increase the extraction selectivity of calcium ions to more than 95%.

[0055] In other specific embodiments, the volume molar concentration of the ammonium salt in the ammonium salt aqueous solution can be 0.1, 0.2, 0.3, 0.4, 0.5, 1, 1.5, 2, or 2.5 M; the extraction time can be 0.6, 0.7, 0.8, or 0.9 hours, and is not limited thereto.

[0056] In a specific embodiment, the extraction process is to mix converter slag and an ammonium salt aqueous solution in a mixing tank with a stirring device, and optionally adjust the pH value of the solution to more than 8.0 by adding an alkali solution, and then obtain the reaction solution after solid-liquid separation, wherein the alkali solution can be selected from ammonia water or sodium hydroxide.

[0057] In another specific embodiment, the pH value of the reaction solution is 8.0 to 11.0. In other embodiments, the pH value of the reaction solution can be 8.5, 9.0, 9.5, 10.0, or 10.5, and is not limited thereto.

[0058] In another specific embodiment, the extraction process includes: under the conditions of a mixing tank with a temperature of 15 to 40 °C and normal pressure, mixing converter slag and an ammonium salt aqueous solution, dispersing or dissolving the converter slag material in the ammonium salt aqueous solution to carry out the calcium ion extraction process until the pH value of the solution reaches more than 8.0 and no longer changes, and then removing the solid components by suction filtration or centrifugal filtration, and the extraction liquid is the reaction solution for the precipitation reaction.

[0059] In the text, the "ammonium salt" is a compound composed of ammonium ions and acid radical ions, and its non-limiting examples include one or more compounds selected from the group consisting of ammonium chloride, ammonium nitrate, and ammonium acetate.

[0060] In the text, the "basic-oxygen-furnace slag" is a slag by-product generated during the basic oxygen furnace stage of steel and iron smelting, and it contains elements such as calcium, magnesium, barium, and phosphorus, among which the calcium content is 20% by weight or more. In a specific embodiment, the particle size of the basic-oxygen-furnace slag used in the present disclosure is less than or equal to 1000 microns. In other specific embodiments, the particle size of the basic-oxygen-furnace slag can be 50, 75, 100, 125, 150, 177, 200, 250, 300, 400, 500, 600, 700, 800, or 900 microns, and is not limited thereto.

[0061] In the preparation method of the present disclosure, since the basic-oxygen-furnace slag generated from steel and iron smelting is used as the preparation raw material, it has a more competitive advantage in terms of raw material cost compared with the prior art.

[0062] In the text, the "reaction solution" contains calcium ions, magnesium ions, and barium ions, and the calcium ion concentration is 0.1 to 5% by weight, the molar ratio of calcium ions to magnesium ions is 300 to 1000, and the molar ratio of calcium ions to barium ions is 30000 to 70000. If barium ions or magnesium ions are lacking in the reaction solution, the structure of the prepared calcium carbonate particles is in a spherical form; if the ratio among magnesium ions, barium ions, and calcium ions in the reaction solution is not within the above range, the structure of the prepared calcium carbonate particles is partially in a rod shape, partially in a spherical shape, and partially in a cubic shape, the overall morphology has poor uniformity, and its particle size distribution is also not easy to control.

[0063] In other embodiments, the calcium ion concentration can be 0.2, 0.4, 0.6, 0.8, 1, 2, 3, or 4% by weight, and is not limited thereto.

[0064] In the preparation method of the present disclosure, the "precipitation reaction" is to form an insoluble calcium carbonate product by the combination of calcium ions and carbonate ions in a liquid phase system. In one embodiment, the precipitation reaction is carried out at 15 to 40 °C, and the pressure does not need to be controlled and can be carried out at normal pressure, for example, at a state of 1 atm. In other embodiments, the temperature of the precipitation reaction can be 17, 20, 22, 23, 24, 25, 26, 27, 28, 29, 30, or 35 °C, and is not limited thereto.

[0065] Regarding the "high-gravity reaction device" used for the precipitation reaction, it is shown as Figure 2 shown.

[0066] As Figure 2As shown, the device structure of the high-gravity reaction device 1 includes: a housing 10; a rotating disk 11 disposed at the center of the inner cavity of the housing 10. Among them, corresponding to the surface of the rotating disk 11, a plurality of nozzles are provided so that the reaction solution forms a liquid film layer on the rotating disk 11. In one embodiment, the radius of the rotating disk 11 is 5 to 200 cm or 5 to 50 cm, and the opening size of the nozzle is 3 to 100 mm; a motor transmission member 12 connected to the rotating disk 11; an infusion tube 13 for introducing the reaction solution and communicating with the rotating disk 11; a feed port 14 for feeding the carbon source and a drain pipe 15 for discharging the calcium carbonate slurry.

[0067] In a specific embodiment, the calcium carbonate slurry discharged through the drain pipe 15 can be repeatedly refluxed by a pump and re-introduced into the high-gravity reaction device 1 through the infusion tube 13 to extend the precipitation reaction time and make the reaction more complete; in the present disclosure, the precipitation reaction time is greater than 0 to 60 minutes.

[0068] In other specific embodiments, the precipitation reaction time can be 10, 15, 20, 25, 30, 35, 40, 45 or 50 minutes, and is not limited thereto.

[0069] The method for preparing rod-shaped calcium carbonate provided by the present disclosure is to feed the reaction solution onto the rotating disk 11 through the infusion tube 13, and rotate the rotating disk 11 at a speed of 300 to 600 rpm through the motor transmission member 12 of the high-gravity reaction device 1; at the same time, feed the carbon source into the high-gravity reaction device 1 through the feed port 14, and under the conditions of a temperature of 15 to 40 °C and normal pressure, make the carbon source and the reaction solution fully contact on the rotating disk 11 and carry out a precipitation reaction; the calcium carbonate slurry formed by the reaction further flows to the inner wall surface of the housing by gravity and is discharged through the drain pipe 15.

[0070] In a specific embodiment, the flow rate of the reaction solution fed into the reaction tank is 1.2 to 1.6 L / min; in other embodiments, the flow rate of the reaction solution fed into the reaction tank can be 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55 or 1.6 L / min, and is not limited thereto.

[0071] In addition, upstream of the high-gravity reaction device, a carbon source supply device can be set and connected to provide a stable carbon source in a batch or continuous manner and carry out a precipitation reaction when the reaction solution is fed into contact.

[0072] In a specific embodiment, the flow rate of the carbon source fed into the reaction tank is 1 to 5 L / min; in other embodiments, the flow rate of the carbon source fed into the reaction tank can be 1.5, 2, 2.5, 3, 3.5, 4 or 4.5 L / min, and is not limited thereto.

[0073] In the preparation method of the present disclosure, the "carbon source" includes a carbon dioxide-containing mixed gas, a carbonic acid aqueous solution, or a carbonate aqueous solution.

[0074] In the text, the "carbonic acid aqueous solution" can be prepared by injecting carbon dioxide into water through an aeration device for carbonation reaction, or by dissolving a carbonate compound in water.

[0075] In the text, the "carbon dioxide" can be obtained not only by collecting it from the air, but also by integrating with other processes to capture carbon dioxide in industrial tail gas for further utilization, while achieving the purpose of reducing carbon emissions.

[0076] In a specific embodiment, the carbon source is a carbon dioxide-containing mixed gas, and the concentration of carbon dioxide accounts for 80 to 100% of its total volume. Other gases can be exemplified by nitrogen; in other specific embodiments, the concentration of carbon dioxide can account for 82, 84, 86, 88, 90, 92, 94, 96, or 98% of its total volume, and is not limited thereto.

[0077] When using the "carbon dioxide-containing mixed gas" as the carbon source, since the carbon source and the reaction solution are in the gas phase and the liquid phase respectively, during the precipitation reaction, it is also subject to the progress of the carbonation reaction. Therefore, to improve the reaction rate and conversion rate, the reaction tank used in the present disclosure has the function of enabling sufficient gas-liquid phase contact. The contact forms of the gas-liquid phase include: making the carbon source gas flow in the same or opposite direction to contact the liquid film layer formed by the reaction solution, but not limited thereto.

[0078] In addition, the carrier gas used in the mixed gas of the present disclosure is mainly nitrogen, and it does not affect the progress of the overall carbonation reaction and precipitation reaction.

[0079] In a specific embodiment, the preparation method includes: mixing converter slag and an ammonium salt aqueous solution (the volume molar concentration of the ammonium salt is 0.01 to 3M) for extraction, removing the insoluble substances in the extraction process to obtain a reaction solution containing calcium ions, magnesium ions, and barium ions, and the calcium ion concentration is 0.1 to 5% by weight; then, feeding the reaction solution to the rotating disk 11 through the infusion tube 13 at a flow rate of 1.2 to 1.6 liters per minute, and rotating the rotating disk 11 at a speed of 300 to 600 rpm through the motor driving member 12 of the high-gravity reaction device 1 at a temperature of 15 to 40 °C, so that the reaction solution forms a liquid film layer on the rotating disk 11; at the same time, feeding the carbon source into the high-gravity reaction device 1 through the feed port 14, so that the carbon source and the reaction solution are in full contact on the rotating disk 11 and a precipitation reaction occurs to form a calcium carbonate slurry. By controlling the above operating conditions, the process of the present disclosure can obtain rod-shaped calcium carbonate with high purity without using other additional additives (such as: crystal form control agents or crystal seeds).

[0080] Regarding the "separation" procedure after the precipitation reaction of the present disclosure, gas extraction drying or centrifugation can be used for solid-liquid separation.

[0081] In a specific embodiment, the temperature of gas extraction drying is 15 to 40 °C.

[0082] In another specific embodiment, the method for preparing rod-shaped calcium carbonate of the present disclosure further includes returning the separated liquid to the extraction process as an extraction solvent. Please refer to Figure 3 , which illustratively shows a schematic diagram of a reaction system with a high-gravity reaction device, including: a high-gravity reaction device 1; a carbon source supply device 2, arranged upstream of the high-gravity reaction device 1 and connected by a pipeline to feed into its feed port 14; a mixing tank 31 for performing the extraction process, arranged upstream of the high-gravity reaction device 1. After the extraction is completed, the solid components are removed by a solid-liquid separation device 32, and its extraction liquid is connected by a pipeline to feed into its liquid delivery pipe 13; a solid-liquid separation device 4, connected through the drain pipe 15 of the high-gravity reaction device 1, for treating the calcium carbonate slurry after the reaction; after the separation treatment by the solid-liquid separation device 4, the separated liquid is returned to the mixing tank 31 of the extraction process, and rod-shaped calcium carbonate 5 is obtained.

[0083] In addition, the method for preparing rod-shaped calcium carbonate of the present disclosure may further include performing reprecipitation treatment on the separated liquid.

[0084] Please refer to Figure 4 , which illustrates another preparation method flow of the rod-shaped calcium carbonate of the present disclosure. First, converter slag and ammonium salt aqueous solution are mixed for extraction (step S21); then, the insoluble substances in the extraction are removed to obtain a reaction solution containing calcium ions, magnesium ions and barium ions (step S22); in a high-gravity reaction device with a rotational speed of 300 to 600 rpm, the reaction solution and the carbon source are subjected to a precipitation reaction (step S23) to form a calcium carbonate slurry; the liquid of the calcium carbonate slurry is separated and subjected to reprecipitation treatment (step S24); and the liquid of the calcium carbonate slurry after the reprecipitation treatment is separated, and rod-shaped calcium carbonate is obtained (step S25).

[0085] This "reprecipitation treatment" allows the separated liquid to stand for a period of time in an environment with a temperature of 15 to 40 °C and normal pressure in a batch manner, and the reprecipitation time is greater than 0 to 24 hours.

[0086] In the present disclosure, since the concentrations of calcium ions, magnesium ions and barium ions extracted and dissolved are related to the particle size of the converter slag; when the particle size of the converter slag is less than 500 microns, the obtained reaction solution has a higher concentration of calcium ions, magnesium ions and barium ions. If only relying on the precipitation reaction, the obtained calcium carbonate particles are in a disordered calcite form with poor morphology uniformity. Therefore, it is necessary to optimize the crystal lattice arrangement of its calcium carbonate through reprecipitation treatment to obtain a calcium carbonate product with a rod-shaped morphology.

[0087] Please refer to Figure 5 which is a schematic diagram of an exemplary reaction system with a supergravity reaction device, including: a supergravity reaction device 1; a carbon source supply device 2, disposed upstream of the supergravity reaction device 1 and connected by a pipeline to feed into its feed port 14; a mixing tank 31 for performing an extraction process, disposed upstream of the supergravity reaction device 1. After the extraction is completed, the solid components are removed by a solid-liquid separation device 32, and its extract is connected by a pipeline to feed into its infusion pipe 13; a solid-liquid separation device 4, connected through the drain pipe 15 of the supergravity reaction device 1, to process the calcium carbonate slurry after the reaction; after the separation treatment by the solid-liquid separation device 4, the separated liquid is transferred to a sedimentation tank 51 for reprecipitation treatment; after the reprecipitation treatment is completed, separation treatment is performed by a solid-liquid separation device 52, and the separated liquid is refluxed to the mixing tank 31 of the extraction process, and thus rod-shaped calcium carbonate 6 is obtained.

[0088] As can be seen from the above, since the manufacturing methods of the present disclosure do not use any additives (such as crystal form control agents or seeds), and the solvent components are simple, the separated liquid can be recovered and reused, which is beneficial to reducing the overall process cost.

[0089] The rod-shaped calcium carbonate prepared by the present disclosure according to the above method, by observing its surface morphology through a scanning electron microscope (SEM), has an average length of 4 to 25 microns, and its aspect ratio is 3 to 25.

[0090] In other specific embodiments, the length of the rod-shaped calcium carbonate can be 5, 7, 10, 12, 15, 17, 20 or 22 microns, and is not limited thereto.

[0091] The rod-shaped calcium carbonate provided by the above manufacturing method can be applied to the fields of papermaking, rubber or plastics. Due to its high aspect ratio and high purity characteristics, when used as a filler or coating in the fields of papermaking, plastics, rubber, etc., it can help improve the printability, gloss and strength of the product.

[0092] The following further details the present disclosure through specific examples, but the scope of the present disclosure is not limited by the description of the examples.

[0093] Example 1: Preparation of rod-shaped calcium carbonate

[0094] Using Figure 3 the reaction system and the following process to prepare rod-shaped calcium carbonate.

[0095] Extraction treatment: At room temperature (about 25 °C), in a mixing tank equipped with a blade stirrer with a stirrer speed of 400 rpm, under normal pressure, 100 grams of converter slag (particle size 500 to 1000 microns) was dissolved in 500 ml of 1M ammonium chloride aqueous solution for extraction treatment for 0.5 to 1 hour. After the extraction was completed, the undissolved solid components were removed by suction filtration or centrifugal filtration. The clarified extraction solution was the reaction solution, with a pH value of 9.8, a calcium ion concentration of 0.6745 wt%, a molar ratio of calcium ion to magnesium ion of 395.98, and a molar ratio of calcium ion to barium ion of 32689.81.

[0096] Precipitation reaction: Using Figure 2 the high-gravity reaction device as the reaction tank for the precipitation reaction, the reaction solution was fed to the rotating disk 11 (the radius of the rotating disk was about 6 cm) through the infusion tube 13 at a flow rate of 1.5 liters per minute, and the opening size of the nozzle on the rotating disk was about 3 mm; through the motor drive 12 of the high-gravity reaction device 1, the rotating disk 11 was rotated at a speed of 400 rpm to form a liquid film layer of the reaction solution on the rotating disk 11.

[0097] At the same time, using carbon dioxide gas as the carbon source, the carbon source was fed into the high-gravity reaction device 1 through the feed port 14 at a flow rate of 1 liter per minute. Under the conditions of a temperature of 25 °C and normal pressure, the carbon source was brought into contact with the reaction solution for the precipitation reaction to form a calcium carbonate slurry.

[0098] The calcium carbonate slurry removed through the drain pipe 15 was refluxed to the high-gravity reaction device 1 through the infusion tube 13 by a pump, and the precipitation reaction was repeated for about 1 minute.

[0099] Separation procedure: The liquid in the calcium carbonate slurry was subjected to solid-liquid separation by suction filtration or centrifugal filtration to obtain calcium carbonate particles.

[0100] Finally, the calcium carbonate particles prepared above were observed for their appearance, structure and measured for their particle size by a scanning electron microscope (Scanning Electron Microscope, SEM). It can be seen that the calcium carbonate particles have a rod-like structure, as Figure 6 shown; analyzed by Image J image analysis software and the results were recorded in Table 1. It can be seen that the length of the rod-like calcium carbonate is in the range of about 5 to 10 microns and the aspect ratio is 4.

[0101] Comparative Example 1: Difference in raw material particle size

[0102] The preparation method and reaction system are the same as those in Example 1, except that converter slag with a particle size of 177 to 500 μm is used. The calcium ion concentration of the reaction solution obtained after extraction is 1.3095 wt %, the molar ratio of calcium ion to magnesium ion is 430.89, and the molar ratio of calcium ion to barium ion is 45004.95. Calcium carbonate particles are obtained after precipitation reaction and separation procedures.

[0103] Next, the calcium carbonate particles obtained above were observed according to the analytical method of Example 1, and the results are recorded in Tables 1 and Figure 7 ; From the results, it can be seen that the calcium carbonate is in block form (particle size is about 10 to 20 microns), and the surface is covered with multiple rod-shaped calcium carbonate particles, whose length is about 2 to 3 microns and the aspect ratio is 5.

[0104] Example 2: Preparation of rod-shaped calcium carbonate

[0105] by Figure 5 The reaction system and the following process were used to prepare the product.

[0106] Extraction treatment: At room temperature (about 25° C.), in a mixing tank 31 equipped with a blade stirrer and a stirrer speed of 400 rpm, 200.08 g of converter slag (particle size 177 to 500 μm) is dissolved in 1 liter of 1M ammonium chloride aqueous solution for extraction treatment for 0.5 to 1 hour under normal pressure. After the extraction is completed, the undissolved solid components are removed by vacuum filtration or centrifugal filtration. The clarified extract is taken and an alkali solution is added to adjust the pH value to be greater than 9.5, thereby obtaining a reaction solution with a calcium ion concentration of 1.3095% by weight, a molar ratio of calcium ions to magnesium ions of 430.89, and a molar ratio of calcium ions to barium ions of 45004.95.

[0107] Precipitation reaction and separation procedure: The precipitation reaction is completed in the supergravity reaction device 1 by the method of Example 1, and solid-liquid separation is performed by vacuum filtration or centrifugal filtration. The obtained solid precipitate is observed by scanning electron microscopy to be a disordered calcite morphology (such as Figure 8A ).

[0108] Reprecipitation treatment: The separated liquid is transferred to a sedimentation tank 51 and reprecipitated for 1 hour at a temperature of 25° C. and normal pressure. After the reprecipitation is completed, solid-liquid separation is performed by vacuum filtration or centrifugal filtration to obtain calcium carbonate particles.

[0109] According to the analytical method of Example 1, the calcium carbonate particles obtained above were observed and the results were recorded in Table 1 and Figure 8B ; From the results, it can be seen that the calcium carbonate has a rod-like structure with a length of approximately 10 to 15 microns and an aspect ratio of 20.

[0110] Example 3: Preparation of rod-shaped calcium carbonate

[0111] The preparation method was the same as that of Example 2, but converter slag with a particle size less than 177 microns was selected as the raw material. After extraction, the calcium ion concentration of the resulting reaction solution was 2.0617 wt%, the molar ratio of calcium ions to magnesium ions was 957.35, and the molar ratio of calcium ions to barium ions was 67152.1; after the precipitation reaction, the obtained solid precipitate was observed by scanning electron microscopy to be in the form of disordered calcite (as Figure 9A ).

[0112] Next, the liquid separated after the precipitation reaction was taken for reprecipitation treatment to obtain calcium carbonate particles. According to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 1 and Figure 9B ; from the results, it can be seen that the calcium carbonate is in a rod-like structure, with a length in the range of about 10 to 20 microns and an aspect ratio of 6.

[0113] Table 1

[0114]

[0115] Comparative Example 2: Difference in reaction device

[0116] The preparation method and reaction system were the same as those of Example 1, but the rotating packed bed reactor was changed to a bubble column reactor.

[0117] The specific operation instructions are as follows: 200 g of converter slag raw material was taken and extracted with 1 L of 1 M ammonium chloride aqueous solution for 0.5 to 1 hour. After solid-liquid separation by suction filtration or centrifugal filtration, the clarified extraction solution was taken and adjusted with ammonia water to make its pH value greater than 9.5, and the calcium ion concentration was 0.6745 wt%, and the molar ratio of calcium ions to magnesium ions was 395.98, which was the reaction solution.

[0118] Next, the reaction solution and carbon dioxide were fed into a bubble column reactor with a magnetic stirrer for precipitation reaction. Among them, the stirring rate of the magnetic stirrer was 100 rpm, and the feeding flow rate of carbon dioxide was 0.3 L / min; at the same time, the generated calcium carbonate slurry was repeatedly refluxed to make the precipitation reaction continue for about 0 to 10 minutes; finally, after solid-liquid separation by suction filtration or centrifugal filtration, calcium carbonate particles were obtained.

[0119] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 3 and Figure 10 ; from the results, it can be seen that the calcium carbonate is spherical, with a particle size in the range of about 1 to 4 microns.

[0120] Comparative Example 3: Difference in raw material composition

[0121] It was prepared with Figure 3 reaction system and the following process.

[0122] Extraction treatment: At room temperature (about 25 °C), in a mixing tank equipped with a blade stirrer and a stirrer speed of 400 rpm, under normal pressure, 2.08 grams of calcium chloride was dissolved in 500 milliliters of 0.2 M ammonium chloride aqueous solution for extraction treatment for 1 hour. After the extraction was completed, the undissolved solid components were removed by suction filtration or centrifugal filtration. The clarified extract was taken and the pH value was adjusted to be greater than 9.5 by adding an alkali solution to obtain a reaction solution, and the calcium ion concentration was 0.15 wt%.

[0123] Precipitation reaction: Using the high-gravity reaction device of Example 1 as the reaction tank for the precipitation reaction, the reaction solution was fed onto the rotating disk at a flow rate of 1 liter / minute; through the motor drive of the high-gravity reaction device, the rotating disk was rotated at a speed of 500 rpm to form a liquid film layer of the reaction solution on the rotating disk.

[0124] At the same time, using carbon dioxide gas as the carbon source, the carbon source was fed into the high-gravity reaction device at a flow rate of 1.5 liters / minute. Under the conditions of a temperature of 25 °C and normal pressure, the carbon source was brought into contact with the reaction solution for precipitation reaction to form a calcium carbonate slurry.

[0125] The calcium carbonate slurry removed through the drain pipe was recycled to the high-gravity reaction device through a pump and the infusion pipe, and the precipitation reaction was repeated for about 0 to 10 minutes.

[0126] Separation procedure: The liquid in the calcium carbonate slurry was subjected to solid-liquid separation by suction filtration or centrifugal filtration to obtain calcium carbonate particles.

[0127] Finally, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 2 and Figure 11 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 0.5 to 2.5 microns.

[0128] Comparative Example 4: Difference in raw material composition

[0129] The preparation method and reaction system were the same as those in Example 1, but 18.59 grams of calcium chloride and 0.096 grams of magnesium chloride hexahydrate were used as raw materials, and 1 liter of 1 M ammonium chloride aqueous solution was used as the extraction solvent. After extraction, the calcium ion concentration of the obtained reaction solution was 0.67 wt%, the molar ratio of calcium ions to magnesium ions was 355, and calcium carbonate particles were obtained after the precipitation reaction and separation procedure.

[0130] Then, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 2 and Figure 12 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 1 to 3 microns.

[0131] Comparative Example 5: Difference in raw material composition

[0132] The preparation method and reaction system are the same as those in Example 1, but 18.59 g of calcium chloride and 0.0114 g of barium chloride dihydrate are used as raw materials, and 1 liter of 1M ammonium chloride aqueous solution is used as the extraction solvent. After extraction, the calcium ion concentration of the reaction solution obtained is 0.67 wt%, the molar ratio of calcium ions to barium ions is 3589, and calcium carbonate particles are obtained after the precipitation reaction and separation procedure.

[0133] Then, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 2 and Figure 13 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 1 to 3 microns.

[0134] Comparative Example 6: Difference in raw material composition

[0135] The preparation method and reaction system are the same as those in Example 1, but 18.59 g of calcium chloride and 0.097 g of sodium dihydrogen phosphate dihydrate are used as raw materials, and 1 liter of 1M ammonium chloride aqueous solution is used as the extraction solvent. After extraction, the calcium ion concentration of the reaction solution obtained is 0.67 wt%, and calcium carbonate particles are obtained after the precipitation reaction and separation procedure.

[0136] Then, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 2 and Figure 14 ; It can be seen from the results that the calcium carbonate has a spherical structure, and its particle size is in the range of about 1.5 to 16 microns.

[0137] Comparative Example 7: Difference in raw material composition

[0138] The preparation method and reaction system are the same as those in Example 1, but 18.59 g of calcium chloride, 0.1012 g of magnesium chloride hexahydrate and 0.0114 g of barium chloride dihydrate are used as raw materials, and 1 liter of 1M ammonium chloride aqueous solution is used as the extraction solvent. After extraction, the calcium ion concentration of the reaction solution obtained is 0.67 wt%, the molar ratio of calcium ions to magnesium ions is 336.76, the molar ratio of calcium ions to barium ions is 3589, and calcium carbonate particles are obtained after the precipitation reaction and separation procedure.

[0139] Then, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 2 and Figure 15 ; It can be seen from the results that the calcium carbonate has spherical, rod-shaped and cubic structures, with uneven morphology, its particle size is in the range of about 1 to 8 microns, and the uniformity is poor.

[0140] Table 2

[0141]

[0142]

[0143] Comparative Example 8: Differences in Raw Material Composition and Reaction Apparatus

[0144] The preparation method was the same as that of Comparative Example 2, but 0.8324 g of calcium chloride, 1.5248 g of magnesium chloride hexahydrate, and 1.832 g of barium chloride dihydrate were used as raw materials, and 100 ml of 0.075 M ammonium chloride aqueous solution was used as the extraction solvent. Therefore, the calcium ion concentration of the reaction solution prepared after extraction was 0.3 wt%, the molar ratio of calcium ions to magnesium ions was 1, and the molar ratio of calcium ions to barium ions was 1; in addition, the feeding flow rate of carbon dioxide was adjusted to 1 L / min to carry out the precipitation reaction, and calcium carbonate particles were obtained after the separation process.

[0145] Finally, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 3 and Figure 16 ; It can be seen from the results that the calcium carbonate was spherical and rod-shaped, and its particle size was in the range of about 0.7 to 2.2 microns.

[0146] Comparative Example 9: Reprecipitation Treatment

[0147] The parameter settings and apparatus of the extraction process and the precipitation reaction were the same as those of Comparative Example 8. However, after the extraction and precipitation reaction, the liquid separated after the precipitation reaction was taken and subjected to reprecipitation treatment for 0 to 24 hours in an environment at a temperature of 25 °C and normal pressure. After the reprecipitation treatment was completed, solid-liquid separation was carried out by suction filtration or centrifugal filtration to obtain calcium carbonate particles.

[0148] Finally, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 3 and Figure 17 ; It can be seen from the results that the calcium carbonate was spherical and rod-shaped, and its particle size was in the range of about 0.5 to 2.3 microns.

[0149] Table 3

[0150]

[0151] Comparative Example 10: Rotation Speed Difference

[0152] The preparation method was the same as that of Example 1, but an alkali solution was added to the extraction process to make its pH value reach above 9.5, and the rotation speed of the high-gravity reaction apparatus in the precipitation reaction stage was changed to 200 rpm, and calcium carbonate particles were obtained after the precipitation reaction and the separation process.

[0153] Then, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 18 ; It can be seen from the results that the calcium carbonate was spherical, and its particle size was in the range of about 0.75 to 2.3 microns.

[0154] Comparative Example 11: Rotation Speed Difference

[0155] The preparation method was the same as that of Comparative Example 10, but the rotation speed of the high-gravity reaction device in the precipitation reaction stage was changed to 700 rpm, and calcium carbonate particles were obtained after the precipitation reaction and separation procedure.

[0156] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 19 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 1 to 1.8 microns.

[0157] Comparative Example 12: Rotation Speed Difference

[0158] The preparation method was the same as that of Comparative Example 10, but the rotation speed of the high-gravity reaction device in the precipitation reaction stage was changed to 1000 rpm, and calcium carbonate particles were obtained after the precipitation reaction and separation procedure.

[0159] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 20 ; It can be seen from the results that the calcium carbonate is oblate, and its particle size is in the range of about 1.4 to 1.6 microns.

[0160] Comparative Example 13: Rotation Speed Difference

[0161] The preparation method was the same as that of Comparative Example 10, but the rotation speed of the high-gravity reaction device in the precipitation reaction stage was changed to 2000 rpm, and calcium carbonate particles were obtained after the precipitation reaction and separation procedure.

[0162] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 21 ; It can be seen from the results that the calcium carbonate is oblate, and its particle size is in the range of about 1 to 2 microns.

[0163] Comparative Example 14: Reaction Solution Flow Rate Difference

[0164] The preparation method was the same as that of Example 1, but an alkali solution was added in the extraction procedure to make its pH value above 9.5, and the flow rate of the reaction solution fed in the precipitation reaction stage was changed to 0.2 L / min, and calcium carbonate particles were obtained after the precipitation reaction and separation procedure.

[0165] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 22 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 1 to 2 microns.

[0166] Comparative Example 15: Reaction Solution Flow Rate Difference

[0167] The preparation method was the same as that of Comparative Example 14, but the flow rate of the reaction solution fed in the precipitation reaction stage was changed to 0.5 L / min, and calcium carbonate particles were obtained after the precipitation reaction and separation procedures.

[0168] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 23 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 0.73 to 1.7 microns.

[0169] Comparative Example 16: Difference in reaction solution flow rate

[0170] The preparation method was the same as that of Comparative Example 14, but the flow rate of the reaction solution fed in the precipitation reaction stage was changed to 1 L / min, and calcium carbonate particles were obtained after the precipitation reaction and separation procedures.

[0171] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 24 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 1 to 1.5 microns.

[0172] Comparative Example 17: Difference in reaction solution flow rate

[0173] The preparation method was the same as that of Comparative Example 14, but the flow rate of the reaction solution fed in the precipitation reaction stage was changed to 1.8 L / min, and calcium carbonate particles were obtained after the precipitation reaction and separation procedures.

[0174] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 25 ; It can be seen from the results that the calcium carbonate is spherical, and its particle size is in the range of about 0.4 to 3 microns.

[0175] Comparative Example 18: Difference in carbon source flow rate

[0176] The preparation method was the same as that of Example 1, but the flow rate of the carbon source fed in the precipitation reaction stage was changed to 0.5 L / min, and calcium carbonate particles were obtained after the precipitation reaction and separation procedures.

[0177] Next, according to the analysis method of Example 1, the above-prepared calcium carbonate particles were observed, and the results were recorded in Table 4 and Figure 26 ; It can be seen from the results that the calcium carbonate is oblate, and its particle size is in the range of about 1.4 to 1.8 microns.

[0178] Table 4

[0179]

[0180] In summary, through the operation of the supergravity device and the selection of raw materials, the process of the present disclosure can produce high-purity rod-shaped calcium carbonate at normal temperature and pressure without using any additives (such as crystal form control agents or seeds). Moreover, since no additives (such as crystal form control agents or seeds) are used in the preparation method of the present disclosure and the solvent composition is simple, the solvent can be recovered and reused, and the process improvement effect can be achieved.

[0181] On the other hand, the raw materials of the preparation method of the present disclosure are by-products generated from steel smelting, so it has a more competitive advantage in terms of raw material cost compared with the prior art.

[0182] Generally speaking, the preparation process of the rod-shaped calcium carbonate preparation method of the present disclosure is simple, environmentally friendly, and there is no concern about the residue of additives in its products. Therefore, it has application prospects and industrial application value in many fields such as rubber, plastics, papermaking, printing ink, coatings, and medicine.

[0183] The above embodiments are only illustrative and not intended to limit the present disclosure. Any person skilled in the art can modify and change the above embodiments without departing from the spirit and scope of the present disclosure. Therefore, the scope of the rights protected by the present disclosure is defined by the appended claims of the present disclosure, and should be covered by the technical content of this disclosure as long as it does not affect the effect and implementation purpose of the present disclosure.

Claims

1. A method for preparing rod-shaped calcium carbonate, comprising: mixing converter slag and an ammonium salt aqueous solution for extraction, wherein the particle size of the converter slag is less than or equal to 1000 microns; removing insoluble substances in the extraction process to obtain a reaction solution containing calcium ions, magnesium ions and barium ions, wherein the concentration of the calcium ions is 0.1 to 5% by weight, the molar ratio of the calcium ions to the magnesium ions is 300 to 1000, and the molar ratio of the calcium ions to the barium ions is 30000 to 70000; in a high-gravity reaction device with a rotational speed of 300 to 600 rpm, bringing the reaction solution into contact with a carbon source for a precipitation reaction to form a calcium carbonate slurry; and separating the liquid in the calcium carbonate slurry to obtain the rod-shaped calcium carbonate.

2. The preparation method according to claim 1, wherein the ammonium salt comprises one or more compounds selected from the group consisting of ammonium chloride, ammonium nitrate and ammonium acetate.

3. The preparation method according to claim 1 or claim 2, wherein the volume molar concentration of the ammonium salt in the ammonium salt aqueous solution is 0.01 to 3 M.

4. The preparation method according to claim 1, wherein the extraction is carried out for 0.5 to 1 hour.

5. The preparation method according to claim 1, wherein the reaction solution does not contain a crystal form control agent or crystal seeds.

6. The preparation method according to claim 1, wherein the pH value of the reaction solution is 8.0 to 11.

0.

7. The preparation method according to claim 1, wherein the flow rate of the reaction solution fed into the high-gravity reaction device is 1.2 to 1.6 liters per minute.

8. The preparation method according to claim 1, wherein the carbon source is a carbon dioxide-containing mixed gas, and the concentration of the carbon dioxide accounts for 80 to 100% of its total volume.

9. The preparation method according to claim 1 or claim 8, wherein the flow rate of the carbon source fed into the high-gravity reaction device is 1 to 5 liters per minute.

10. The preparation method according to claim 1, wherein The supergravity reaction device includes a rotating disk to carry out a precipitation reaction between the reaction solution and the carbon source on the rotating disk under the condition that the temperature is 15 to 40 o °C.

11. The preparation method according to claim 1, wherein the precipitation reaction time is greater than 0 to 60 minutes.

12. The preparation method according to claim 1 further comprises subjecting the separated liquid to reprecipitation in an environment with a temperature of 15 to 40 o °C and normal pressure, wherein the time of the reprecipitation is greater than 0 to 24 hours.

13. The preparation method according to claim 1, wherein the average length of the rod-shaped calcium carbonate is 4 to 25 microns, and the aspect ratio is 3 to 25.

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